Method of treating a ferrous melt with a porous sintered metal body impregnated with a treating agent



METHOD'OF TREATING A FERROUS MELT WITH A POROUS SINTERED METAL BODY Ill/[PREG- NATED WHH A TREATING AGENT Sven Sigvard Bergh, Repelycke,

to Wargiins Aktiebolag, pa y Vargon, Sweden, assignm- Vargon, Sweden, 2 Swedish No-Drawing. Application April 27, 1953 Serial No. 351,515

Claims priority, application Sweden April 28, 1952 6 Claims. (CI. 75-53) An iron-or steelmelt often must'be-subjected to additional: alloying. orrefining treatments in the melting furnace-and'even after the same before the melt can be castztoxingots in moulds. Examples of such after-treatments of the melt are deoxidation, desulfurization, denitrogenizing, dephosphorizing, deslagging, degasing and alloying'but. alsoother treatments may be required by which the content of some non-desirable substance in themelt is removed or decreased to a desired degree. Many of these treatments have been known since. the beginning of production process for the steel or ferroalloys; others have been invented later on when the utilization of impure raw materials has brought about the introduction of non-desired impurities. Modern technique=demands more and more highly alloyed steels and these are. often very difiicult to work in heated as well as in cold condition. It has often turned out that the malleability is unfavorably affected by even very-small contents of impurities which have no influence on the working of simpler steels. In order to decrease or remove such contents of impurities new refining methods havebeen invented for the molten steel and also the addi-. tions to the steel melt, e.g. ferro-alloys, for the same reason should'be refined by means of similar refining processes;

In deoxidizing, desulfurizing, dephosphorizing, denitrogenizing etc; the content of oxygen, sulfur, phosphorus, nitrogen etc. of the melt is to be decreased, and this is performed by means of substances which have a higher aflinity for oxygen, sulfur, phosphorus, nitrogen etc. than for the elements entering intothe steel or alloy. The compounds of oxygen, sulfur, phosphorus and nitrogen formed from, such additions shouldpreferablybe nonsoluble in the meltand should have such a melting point, specific gravity, viscosity etc. that they can easily and as completelytaspossible-be separated from the metal melt and; collected in the slag.

When degasinga melt-the same should be intimately brought into contact which the degasing agent.- This degasing agent generally isa gas and a condition for a good degasificationsis that the partial pressure of the gas constituent to be removedisv low in the purifying gas-and'that the latter-is supplied and distributedinsuch a way that it comes into a most intimate contact with all parts of the melt: Asdegasifying agents there can be used. gases, which. not at all or only very. slowly, react with the main constituents of themelt, e.g. helium, argon, nitrogen etc.' Alternatively. there could be addedto the meltasubstance, suitably, ametabor alloy with a boiling point below the solidifyingtpoint of the. melt, which metal or alloy when contacting the melt is gasified. Such metals or, alloysare, for instance, calcium, silicon-calcium-alloys, magnesiunn nickel-magnesium-alloys I and others. In most cases of the last mentioned examples the additions have a very strong deoxidizing influence and it is even possible that the influence of the metal gas formed at the contact with the melt as a washing agent Patented Apr. 7, 1959 has been. overlooked; Since these last mentioned additionshave a-very low specific gravity, the contact with the melt with certainty will be bad and the degasifying influence incomplete andinsignificant. Blowing of gas into the melt according to the first mentioned alternative is ditiicult to perform in such a manner that gas becomes well distributed and all parts of the melt treated.

The present invention relates to supply bodies for metal melts which make possible an efiective washing of the bath or the melt with gas and/or simultaneously have a strong deoxidizing, desulfurizing, dephosphorizing, denitrogenizing, etc. action and may in someother way exert arefining action and possibly also alloy with the melt.

The supply bodies according to the invention are mainly characterized in that they consist of a porous bodyor skeleton produced from at least oneof the elements of the melt, the pore volume of which is partially or completely filled with a refiningand/oralloying agent. More particularly the supplybody may consist of a skeleton of a solidgporous body of iron or steel or its alloys or of alloying metals intended'for iron and steel alloys, the pore volume. of which is completely or partially filled witha refining substance which at the temperature of the bath or-met, melts and in some cases is gasified so that it is emitted in the bath or melt.

The skeleton may consist of a powderous metal bondedto briquettes or other shaped bodies by means of binding melt.

The refining agent can consistsof an alkali metal, alkaline-earthtmetal, magnesium, zinc or leader of an alloy of such metals or of another chemical element or of a compound having alow meltingpoint in relation to the solidifying: temperature'of the melt orwith no or only insignificant aflinity forthe main constituentsof themelt.

Since the-material of theskeleton consists-of one or more metals, one or more metal alloys, intermetallic compounds, compounds between-metals and metalloids such as carbides, silicides etc. or mixtures of these different' substances, said skeleton, when contacting the melt will be dissolved ordisintegrated without contaminating the. same and it shall furthernot at all' or only to an insignificant degree react with the degasifying or refining agent in such a way that'the purifying action of'this agent is lost. As has already been mentioned the material of the skeleton can be brought to a suitable porous form by briquetting and/orsintering a material which has been crushed to asuitable grain sizeor mechanically or otherwise transformed to chips or particles with or without the addition ofdbinding. agentsxas well asby atomizing or granulating and agglomeration in a manner known per set Especially-1 suitable for the treatment ,of'steel melts are shaped bodies produced from: iron powder: and/ or comminuted ferro-alloys or mixtures of these substances and produced with or withoutthe addition'of bindingagents, which shaped bodies-have been sintered by heating to a suitable temperature in: a protecting gas. Such sintering is advantageous since the shaped body thus acquires suflicienflmechanicalstrength to resist'the often relatively high internal pressures occurring when the refining agent enclosedin the pores of the shapedbody is gasified. Thegrain sizeof' the ntaterial from which the shaped-' bodies are made -is' of a certainimportance. If a finely grained materialis usedwhepores become so small that= the impregnation is very time-consuming. Further,- the' heated-'=body then becomes unnecessarily expensive. Coarser material results in bigger pores which may be disadvantageous, since the degasifying or refining agent in such a case can be emitted too rapidly after the addition to the melt. A suitable grain size for most purposes is 0.05-1 mm., but coarser as well as finer grains can be used. The porosity in percent should not be too high since the specific gravity of the impregnated shaped bodies would be undesirably low. If on the other hand a greater porosity is required in order to make possible or facilitate the impregnation, the refining agent can be alloyed with a heavier substance in order to avoid a too low specific gravity of the shaped body. The porosity can vary between and 70% but should suitably be between 15 and 50%. As an example a silicon iron briquette with 30% porosity can be mentioned. If such a briquette is impregnated with magnesium, the specific gravity becomes about 5.0. If the same briquette is instead impregnated with a magnesium-zinc-alloy the specific gravity becomes about 5.5. Magnesium melts at 650 C. and is then relatively viscous. The magnesiumzinc-alloy in this example melts at 341 C. and is free flowing. Consequently, the impregnation is much simpler to perform in the latter case.

The refining agent is introduced into the skeleton by impregnating in gaseous or liquid form. In the latter case pieces of the skeleton material are introduced into a melt, consisting of or containing the refining agent or into a solution of the same at a suitable temperature, or the solution or melt can be pressed under suitable pressure through suitable guiding means against one or more surfaces of the porous skeleton body which should then have a suitable regular form. In order to facilitate the penetration into the porous skeleton of substance according to the first mention alternative, the pore system can be evacuated before the refining agent is supplied, or the pore system can be filled with a gas which reacts with and is consumed by the refining agent during its penetration into the pore system. If the refining agent is of such a kind that it is attached or harmed by the constituents of air the above mentioned treatments should be carried out in a suitable protecting gas and the impregnated lumps should be treated in such a way that they are protected against the influence of air, e.g. by coating with a protecting layer of a film-forming material such as paraffine or the like.

Below some examples are given of supply bodies according to the invention:

(1) A sintered sponge iron briquette with 30% porosity is filled with metallic sodium to a net specific gravity of about 5.7. The sodium content is about 5%. 1 kg. of this sodium impregnated briquette delivers about 325 litres of sodium gas at 760 mm. pressure and 1600 C. temperature.

(2) A sintered silicon iron briquette with 40% porosity is filled with sodium. The silicon content is about 22%, sodium content about and specific gravity about 4.3. 1 kg. of this sodium-filled briquette delivers about 750 litres of sodium gas at 760 mm. pressure and 1600 C. temperature.

(3) A sintered silicon-iron briquette with 40% porosity is filled with magnesium. The silicon content is about 20%, magnesium content about and specific gravity 4.6. 1 kg. of this magnesium impregnated briquette delivers about 1000 litres of magnesium gas at 760 mm. pressure and 1600 C. temperature.

(4) A sintered silicon-iron briquette with porosity is filled with calcium-magnesium. The silicon content is about 24%, magnesium content about 5%, calcium content about 1% and specific gravity about 5.5.

(5) A sintered silicon-iron briquette with 30% porosity is filled with calcium-zinc. The silicon content is about 20%, calcium content about 7.5%, zinc content about 6% and specific gravity about 5.2.

(6) A sintered silicon-iron briquette with 30% porosity is filled with magnesium-zinc. The silicon content is about 20%, magnesium content 7.5%, zinc content about 9% and specific gravity 5 .5

(7) A sintered silicon-manganese briquette with 30% porosity is filled with sodium. The silicon content is about 18.5%, manganese content about sodium content about 6.5% and specific gravity about 4.65.

(8) A sintered nickel briquette with 30% porosity is filled with sodium. The nickel content is about 95%, sodium content about 5% and specific gravity about 6.45.

Examples 1-3 above are suitable for deslagging and degasifying steel, Example 4 for the production of so called nodular cast iron, Examples 46 for desulfurizing and dephosphorizing pig iron, Example 7 for deslagging steels for roller bearings and Example 8 for deslagging and purifying nickel, high alloyed nickel steels, corrosion resistant steels, etc.

The invention also involves a method for producing the above described shaped bodies which is mainly characterized in that a strong porous shaped body is first produced as a skeleton after which the pore volume of this body is completely or partially filled with the refining agent.

I claim:

1. The method of treating molten cast iron which comprises introducing into said molten cast iron a porous sintered iron body the pores of which are at least partly filled with magnesium. 2. The method of treating a molten metal selected from the group consisting of iron, pig iron, steel, ferro alloys, nickel and nickel steels which comprises introducing into said molten metal a porous sintered metal body comprising a metal selected from said group, said porous body having its pores at least partially filled with a treating agent having a melting point below the temperature of said molten metal and comprising a metal selected from the group consisting of the alkali metals, the alkaline earth metals, magnesium, zinc and lead.

3. The method as defined in claim 2 in which the porous sintered metal body has a porosity of from 5% to 4. The method as defined in claim 2 in which the treating agent comprises a refining agent for the molten metal.

5. The method as defined in claim 2 in which the treating agent comprises an alloying agent for the molten metal.

6. The method as defined in claim 2 in which the treating agent has a boiling point which is below the tem perature of the molten metal.

References Cited in the file of this patent UNITED STATES PATENTS 1,506,246 McMahon Aug. 26, 1924 1,555,978 Hunt Oct. 6, 1925 1,902,478 Wiegand Mar. 21, 1933 2,485,760 Millis et al. Oct. 25, 1949 2,527,037 Smalley Oct. 24, 1950 FOREIGN PATENTS 29,628 Great Britain Aug. 7, 1919 of 1913 OTHER REFERENCES Abridgments of Specifications, Class 82(i), Period A.D. 1909-15, page 183, publ. by His Majestys Sta tionery Office, London (1921).

Principles of Powder Metallurgy (Jones), published by Edward Arnold & Co. (London), 1943 (page 60 relied on).

Metal Powder Report, vol. 3, No. 1, page 5, edited by Jones et 211., published in 1948. 

2. THE METHOD OF TREATING A MOLTEN METAL SELECTED FROM THE GROUP CONSISTING OF IRON, PIG IRON, STEEL, FERRO ALLOYS, NICKEL AND NICKEL STEELS WHICH COMPRISES INTRODUCING INTO SAID MOLTEN METAL A POROUS SINTERED METAL BODY COMPRISING A METAL SELECTED FROM SAID GROUP, SAID POROUS BODY HAVING ITS PORES AT LEAST PARTIALLY FILLED WITH A TREATING AGENT HAVING A MELTING POINT BELOW THE TEMPERATURE OF SAID MOLTEN METAL AND COMPRISING A METAL SELECTED FROM THE GROUP CONSISTING OF THE ALKALI METALS THE ALKALINE EARTH METALS MAGNESIUM,ZINC AND LEAD. 